Fan



Patented Feb. 18, 1936 PATENT OFFICE FAN Albert A. Criqui, Buflalo, N. Y., assignor to Buffalo Forge Company, Bufl'alo, N. Y.,'a corporation of New York Application July 26, 1934, Serial No. 737,055

10 Claims. (Cl. 170-159) My invention relates in general to fans and more particularly to fans of the disk' type.

It is well known to those skilled in the art that in disk fans of the prior art,v whether equipped with ordinary flat, angularly arranged blades or modifications thereof, the portions of the blades at the outside of the wheel produce greater velocity of the air than do the portions of the blades at the inside of the wheel. This'is due to the fact that-the lineal velocity of the outer portions of the blades is greater than that at the inner portions thereof. I

The principal object of my invention has been to overcome the above disadvantage and to provide a fan of this type in which the velocity of air produced thereby shall be more uniform throughout the length of the blade.

Another'object has been to accomplish this result by a relatively slight and inexpensive change in the blade design.

Moreover, it has been an object to provide a blade for disk fans which shall have its advance edge so formed as to aid in reducing the shock of impact with the air andalso to reduce the vacuum on the backside of the blade at this point.

Furthermore, my blades are so designed that the trailing edge will bring about a more uniform velocity throughout the length of the blade.

'The above objects and advantages have been accomplished by the device shown in the accompanying drawing, of which:

Fig. 1 is a face view of a disk fan embodying my trailing edge in diagram.

My fan' comprises the usual hub member 5 which has a disk 6 carried thereby. Suitable means (not shown) are provided for securing. the hub and disk to the shaft of any suitable driving means. The blades let my fan are. shown' as being four in number, but it is obvious that my invention is notlimited to a fan having four blades, since any desired or suitable number may be employed. Each of the blades is preferably carried by a blade arm 8 which is suitably secured to the blade and which has its inner end ,9 twisted so as to give to the blade the proper pitch. These inner ends 9 are secured by any desired means to the disk 6 of the hub.

As above pointed out, it is clear that the lineal velocity of the leading edge of a fan blade of the disk type drops as any point on the blade 5 reaches the center of the wheel or the inner end of the blade. The velocity of air produced by such a fan is, therefore, not uniform. In overcoming this disadvantage, I have provided each blade with a curved portion l5 at the leading edge l N of the blade, as clearly shown in the diagrammatic view of Fig. 3. This curved portion is preferably generated from a cylinder. This cylinder is shown diagrammatically by the dot and dash line I! of Fig. 3. This cylinder has its axis lying ll! in andsubstantially parallel with the dot and dash line It which represents the point of union between the curved portion l5 and the fiat body portion IQ of the blade. Since the dot and dash n line i8 is arranged at an angle with the leading edge It and is so positioned that it terminates at the inner circular edge 20 of the blade, the curved portion l5, therefore, will be at its maximum at the outer curved edge 2! of the blade and will taper off to nothing at the inner curved 5 edge 20 thereof, as clearly shown in Fig. 3. By providing the curved-portion H: at the leading edge of each blade, and by having the maximum length of curvature at the outer circular edge 2|, the velocity of the air at this point in the blade is somewhat reduced. In addition to the reduction of velocity, the shock of impact of the blade with the air is also reduced, and the vacuum produced on the back side of the blade at this point is minimized. The curved portion I 5 of the 5 blade is so proportioned and positioned that a straight line 3l--3l drawn tangent to such surface at the edge of the blade will make an angle with the axis 32-32 of the wheel which is greater than 90 when such angle is measured with that portion of the axis which lies between the point of intersection of the tangential line and the axis, and the rear surface of the blade.

- Another feature of my blade is that the trailing edge 25 thereof is formed with a curved portion 26. This curved portion, as clearly shown in Fig. 3, is also generated from a cylinder represented by the dot and dash line 21, which cylinder is preferably considerably smaller than the cylinder represented by the dot and dash line I! at the leading edge of the blade. The dot and dash line 28.represents the junction between the curved portion 28 at the heel of the blade and the body part l9 thereof. This dot and dash line is arranged at an angle to the trailing edge 25 of the blade so that the portion 28 is wider at its inner end or that end which terminates in the curveti surface 2! of the blade than it is at the outer end. The line is so arranged that it meets and joins the trailing edge 25 at the outer end or curved surface 2| of the blade so that the curvature at this point is at a minimum. The curved portion 26 is made concave on the face 28 'of the blade, as is the curved portion l5 at the leading edge thereof. Both of these curved portions are, therefore, convex on the back side 30 of the blade. By curving the trailing edge forwardly at the inner end of the blade the air is projected from the blade at varying angles, the greatest angle being near the inner curved end 20 or hub portion of the blade, and the least angle being at the outer end of the blade or curved surface 2i. By curving the trailing edge forwardly at the inner end the usual low velocity at this end of the blade is somewhat compensated for with the result that the flow of air through the blade is much more uniform.

From the foregoing it will be clear that since both curved portions l5 and 26 are concave on the forward or working face of the bladesyand since the curved portions are so arranged that the one on the leading edge is greatest at the outer end of the blade and the one on the trailing edge is greatest at the inner end thereof, a more uni form flow of air than has heretofore been possible is thus produced.

Obviously, instead of providing curved surfaces at each side of the blade which are wider at one end and tapered to substantially no width at the other end (substantially wedge-shaped in form), I may provide substantially flat, wedge-shaped surfaces arranged at such an angle to the flat body part of the blade as to accomplish substantially the same results.

Furthermore, in some cases, it may be advisable to form the blade with only the leading edge, or, only the trailing edge thereof with the curved portions hereinbefore described, and this, it is understood, is within the scope of my invention.

These and other modifications of the details herein shown and described may be made without departing from the spirit of my invention or the scope of the appended claims, and I do not, therefore, wish to be limited to the exact embodiment herein shown and described, the form shown being merely a preferred embodiment thereof.

Having thus described my invention, what I claim is:

1. A fan having a plurality of blades, each arranged at an angle to the axis of the fan, each blade having a curved heel portion at the trailing edge of the blade, such heel portion curving upwardly toward the working face of the blade and being wider at the inner end of the blade than at the outer end thereof.

2. A fan having a plurality of blades, each blade being wider at its outer edge than at its inner edge and each arranged at an angle to the axis of the fan, each blade having a substantially flat body portion and a curved portion at its leading edge, such curved portion extending forwardly toward the working face of the blade, and a curved heel portion at the trailing edge of the blade, such heel portion curving upwardly toward the working face of the blade and being wider at the inner end of the blade than at the outer end thereof. I

3. A fan having a plurality of blades, each arranged at an angle to the axis of the fan, each blade being preferably tapered in formation,

having its outer end wider than its inner end, and each blade having a curved portion at its leading edge, and a curved heel portion at the trailing edge of the blade, said heel portion being formed as a part of a cylinder having its axis arranged 5 at an angle to the trailing edge of the blade, whereby the curved portion of the inner end of the blade is wider than that at the outer end of the blade.

4. A fan having a plurality of blades, each 10 arranged at an angle to the axis of the fan, each blade having a curved portion at its leading edge, and also a curved heel portion at its trailing edge, each of these curved portions being extended upwardly from the working face of the blade, said 15 curved portion at the leading edge being wider at the outer end of the blade and narrower at the irmer end, and the heel portion being wider at the inner end of the blade and narrower at the outer end of the blade, whereby the air velocity will be 20 more uniformly distributedalong the length of the blade.

5. A fan having a plurality of blades, each arranged at an angle to the axis of the fan, each blade having a curved portion at its leading edge, v25 and also a curved heel portion at its trailing edge, each of these curved portions being extended upwardly from the working face of the blade, said curved portion at the leading edge being wider at the outer end of the blade and narrower at the v30 inner end, and the heel portion being wider at the inner end of the blade and narrower at the outer end of the blade, each of such curved portions being developed from separate cylinders, the axis of each of which is arranged at an angle .35 to the edge of each portion, whereby the surface at the leading edge is wider at the outer end of the blade and the surface at the trailing edge is wider at the inner end of the blade.

6. A fan having a plurality of blades, each ar- '4 ranged at an angle to the axis of the fan, each blade having a flat body portion and a curved portion at its leading edge, said curved portion being concave on the forward working face of the blade and being wider at the outer end of the 45 blade and narrower at the inner end thereof, the curvature of the edge portion being such that a line drawn tangent thereto at the outer edge of the blade makes an angle with the axis of the fan which, when measured with that portion of the 50 axis which lies between the back surface of the blade and the point of intersection of the tangential line and the axis, is greater than 7. A fan having a plurality of blades, each arranged at an angle to the axis of the fan, each 55 blade having a curved portion at its leading edge, the curved surface being concave on the working face of the blade and formed as a part of a cylinder, the axis of which is arranged at an angle to the leading edge, so that the curved 60 portion is wider at the outer end of the blade and narrower at the inner end thereof, the curvature of the edge portion being such that a line drawn tangent thereto at the outer edge of the blade makes an angle with the axis of the fan which, 65 when measured with that portion of the axis which lies between the back surface of the blade and the point of intersection of the tangential line and the axis, is greater than 90.

8. A fan having a plurality of blades, each 70 arranged at an angle to the axis of the fan, each blade having a flat body portion and also having a curved portion at its leading edge, the curved surface being concave on the working face of the blade and formed as a part of a cylinder, the axis 75 of the cylinder being arranged at an angle to the leading edge of the blade and substantially coincident with the line of union between the curved portion and the flat body surface of the blade, so that the curved portion is wider at the outer end of the blade and narrower at the inner end thereof, the curvature of the edge portion being such that a line drawn tangent thereto at the outer edge of the blade makes an angle with the axis of the fan which, when measured with thatportion of the axis which lies between the back surface of the blade and the point of intersection of the tangential line and the axis, is greater than 90.

I 9. A fan having a plurality of blades, each arranged at an angle to the axis of the fan, each blade having a curved portion at its leading edge, such curved portion extending forwardly toward the working face of the blade, and a curved heel portion at the trailing edge of the blade, such heel portion curving upwardly toward the working face of the blade, the surfaces of the curved portions beingformed as a part of two cylinders having their axes obliquely arranged. I

10. A fan having a plurality of blades, each arranged, at an angle to the axis of the fan, each end ofv the blade is wider than that at the outer end of the blade.

ALBERT A. CRIQUI. 

